A tube sheet forging reforging process

Abstract

The invention discloses a tube sheet forging reforging process, comprising the following steps: (1) using a heating device to heat a tube sheet forging with internal defects; (2) covering a heat preservation layer on the surface of the heated tube sheet forging, using a forging device to forge the tube sheet forging, each time the forging device forges the tube sheet forging, the height deformation of the tube sheet forging needs to be greater than or equal to 10%, and the holding time is greater than or equal to 10 minutes, so that the internal defects of the tube sheet forging are welded; (3) using a heating device to heat the tube sheet forging after forging, so that the atoms at the welding position inside the tube sheet forging diffuse, and cooling after heating; (4) performing post-forging heat treatment on the cooled tube sheet forging. The invention can reforge tube sheet forgings with macro defects such as looseness and shrinkage holes in the central part, so that macro defects such as looseness and shrinkage holes are formed and welded, so as to improve defects and reduce scrap, so as to reduce costs and save resources.

Description

Technical Field

[0001] The invention relates to the technical field of hot working technology of tube sheet forgings, in particular to a reforging technology of tube sheet forgings. Background Art

[0002] Tube sheet forgings are solid forgings. They are mainly used in pressure vessel equipment, and the main function of tube sheet forgings is to support and fix the tubes in the pressure vessel equipment.

[0003] Large-sized tube sheet forgings usually use die-cast steel ingots as raw materials, which need to go through metallurgical and forging processes to obtain tube sheet forgings. Since tube sheet forgings are solid forgings, the center of the tube sheet forgings usually has macro defects such as looseness and shrinkage during the metallurgical and forging processes. Therefore, the tube sheet forgings are difficult to meet the requirements of ultrasonic testing and are scrapped, which increases costs and wastes resources.

[0004] Ultrasonic testing uses the influence of the acoustic properties of internal defects in materials on the propagation of ultrasonic waves to non-destructively detect the size, shape, and distribution of internal defects in materials. During ultrasonic testing, the defects in the center of the tube sheet forging are reflected to the fluorescent screen in the form of defect waves through ultrasonic waves. The waveform and amplitude of the defect wave are related to the shape of the defect. Therefore, the defect situation in the center of the tube sheet forging can be understood based on the defect wave.

[0005] Therefore, how to improve the defects in the center of the tube sheet forgings to reduce scrapping is a technical problem that needs to be solved urgently by technicians in this field. Summary of the invention

[0006] The present invention aims at the above-mentioned deficiencies in the prior art and provides a tube sheet forging reforging process. The present invention can reforge tube sheet forgings having macro defects such as porosity and shrinkage holes in the central part, so that the macro defects such as porosity and shrinkage holes can be formed and welded to improve the defects and reduce scrapping.

[0007] To achieve the above purpose, the invention provides the following technical solutions:

[0008] A tube sheet forging reforging process comprises the following steps:

[0009] (1) Use heating equipment to heat the tube sheet forging with internal defects;

[0010] (2) Cover the surface of the heated tube sheet forging with an insulation layer, and forge the tube sheet forging using a forging machine. Each time the forging machine forges the tube sheet forging, the height deformation of the tube sheet forging needs to be greater than or equal to 10%, and the holding time needs to be greater than or equal to 10 minutes, so that the internal defects of the tube sheet forging can be welded;

[0011] (3) using a heating device to heat the tube sheet forging after forging to diffuse the atoms at the welding position inside the tube sheet forging, and cooling after the heating is completed;

[0012] (4) The cooled tube sheet forging is subjected to post-forging heat treatment.

[0013] Preferably, in the step (1), the temperature of the heated tube sheet forging is 1220-1280°C, and the insulation time of the heated tube sheet forging is ≥A×D; wherein A=1h / 100mm; and D is the thickness of the tube sheet forging, in mm.

[0014] Preferably, in the step (2), the forging equipment comprises an upper anvil for forging the tube sheet forging and a workbench for supporting the tube sheet forging, and the upper anvil covers the defective area inside the tube sheet forging.

[0015] Preferably, the surface of the upper anvil and the surface of the workbench are both flat.

[0016] Preferably, in step (2), the thermal insulation layer is made of rock wool.

[0017] Preferably, in the step (3), the temperature of the tube sheet forging after heating and forging is 1220-1280°C, and the heating and heat preservation time of the tube sheet forging is greater than or equal to 8 hours.

[0018] Preferably, in step (3), air cooling is used for cooling after heating until the surface temperature of the tube sheet forging is 300-500°C.

[0019] Preferably, in the step (4), the post-forging heat treatment includes normalizing treatment and tempering treatment in sequence.

[0020] Compared with the prior art, the invention has the following beneficial effects:

[0021] 1. In step (2) of a tube sheet forging reforging process provided by the present invention, by covering the surface of the heated tube sheet forging with an insulation layer, the heat dissipation of the tube sheet forging can be reduced during the forging process, thereby allowing the atoms inside the tube sheet forging to maintain a high activity for a long time, and then helping to weld defects such as looseness and keyholes during the forging process.

[0022] On the basis of setting the insulation layer, when forging the tube sheet forgings, each forging is maintained for a certain time, and the tube sheet forgings are allowed to have sufficient height deformation. Sufficient height deformation and holding time can be used to make the atomic state of the welding position more stable and firm.

[0023] Therefore, under the combined effect of setting up a thermal insulation layer, having a sufficient pressure holding time, and having a sufficient amount of height deformation, the internal defects of the tube sheet forging can be fully welded, and the internal defects of the tube sheet forging can be healed and improved.

[0024] Heating the welded tube sheet forgings can allow the atoms near the welding position to further diffuse with each other, thereby making the weld firm, improving the strength and quality of the weld, and thus improving the effect of improving defects.

[0025] Therefore, the tube sheet forging reforging process provided by the present invention can reforge tube sheet forgings with macro defects such as looseness and shrinkage holes in the central part, so that the macro defects such as looseness and shrinkage holes can be improved through high-temperature and high-pressure deformation welding, thereby reducing scrapping, thereby reducing costs and saving resources.

[0026] 2. The present invention can improve the activity of atoms by setting the heating temperature of the tube sheet forging to 1220-1280°C in step (1), so that it is more conducive to welding defects in the forging deformation of the subsequent step (2). If the heating temperature is lower than this range, the activity of atoms decreases, which will be unfavorable for welding defects. If the heating temperature is higher than this range, the tube sheet forging will be overheated or overburned, which will significantly reduce the plasticity and impact toughness of the tube sheet forging, thereby hindering the smooth welding of defects and reducing the forging effect.

[0027] 3. The present invention can not only simplify the forging operation and improve the work efficiency, but also improve the reforging effect by allowing the upper anvil to cover the defective area inside the tube sheet forging. If the upper anvil cannot cover the defective range of the tube sheet forging, it is necessary to adjust the position of the tube sheet forging many times, which makes the forging operation cumbersome and reduces the work efficiency. Moreover, the more cumbersome the operation is, the more the temperature of the tube sheet forging is lost, the lower the welding effect is, and thus the reforging effect is reduced.

[0028] 4. The present invention makes the surfaces of the upper anvil and the workbench flat, so that the defects in the center of the forged tube sheet forging can be compacted better and the surface of the forging can be smoother, so as to reduce the subsequent rough machining and fine machining intensity of the tube sheet forging.

[0029] 5. The present invention uses rock wool as the thermal insulation layer in step (2), which makes it easy to obtain materials and saves costs.

[0030] 6. The present invention can increase the atomic activity in the tube sheet forging by heating the tube sheet forging in step (3) to a temperature of 1220-1280°C, so as to facilitate further diffusion of atoms at the welding position, thereby facilitating improved reforging effect. If the temperature is lower than this range, the atomic activity will be reduced, the welding effect will be reduced, and thus the reforging effect will be reduced. If the temperature is higher than this range, overheating or overburning will occur, which will also reduce the reforging effect.

[0031] The present invention allows the heating and heat preservation time of the tube sheet forging to be greater than or equal to 8 hours, thereby avoiding the problem that atoms cannot fully diffuse due to a short heat preservation time, which in turn leads to a reduction in the welding effect of defects and further avoids a reduction in the reforging effect.

[0032] 7. Since air cooling has a fast cooling speed and high efficiency, air cooling after heating in step (3) can improve the efficiency of reforging. By cooling the tube sheet forging to a surface temperature of 300-500°C by air cooling, white spot defects caused by hydrogen atom precipitation due to too low temperature can be avoided, which is also conducive to improving the reforging effect.

[0033] 8. Normalizing and tempering in post-forging heat treatment can refine the grains and improve the quality of forgings. DETAILED DESCRIPTION

[0034] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0035] Embodiment 1:

[0036] In this embodiment, the tube sheet forging adopts die-cast steel ingot as raw material.

[0037] As a casting, the die-cast steel ingot has defects such as looseness and shrinkage holes inside. Looseness and shrinkage holes are common defects of castings, especially in the central part of the casting, which is a high-incidence area for defects such as looseness and keyholes.

[0038] In order to improve the internal defects of the die-cast steel ingot, the die-cast steel ingot needs to be improved by the forging process described below to obtain the tube sheet forging. After the tube sheet forging is obtained, ultrasonic testing is required to determine which tube sheet forgings are unqualified and need to be reforged, and which tube sheet forgings are qualified and do not need to be reforged.

[0039] The specific steps of the forging process for the die-cast steel ingot are as follows:

[0040] (1) Heating the die-cast steel ingot: In order to make the die-cast steel ingot easier to forge, it is necessary to use a heating device to heat the die-cast steel ingot. Heating can improve the plasticity of the die-cast steel ingot, making it easier to forge.

[0041] Specifically, a gas heating furnace can be used as the heating equipment, and the heating temperature of the mold-cast steel ingot is 1210-1250°C.

[0042] According to the JB / T 6052 standard, the austenite transformation temperature of steel is about 960℃. Austenite is soft and easy to deform. After forging in the austenite state, the lattice will be reorganized, reducing the generation of internal stress, which is also conducive to welding internal defects and ensuring the quality of forgings.

[0043] (2) Forging: In order to make the internal structure of the heated die-cast steel ingot more compact and to heal defects such as looseness and keyholes, forging equipment is required to forge the heated die-cast steel ingot.

[0044] Specifically, a hydraulic press may be used as the forging equipment.

[0045] (3) Post-forging heat treatment: Post-forging heat treatment is to refine the grains and eliminate internal stress.

[0046] After the above steps (1)-(3), the defects inside the die-cast steel ingot can be improved, thereby obtaining a tube sheet forging. In addition, the above steps (1)-(3) are conventional processing procedures for processing tube sheet forgings.

[0047] Since the die-cast steel ingot used as the raw material for the tube sheet forging is a solid casting, the above-mentioned forging process may not be able to forge through the center of the die-cast steel ingot, so that the center of the tube sheet forging obtained after forging the die-cast steel ingot is also prone to defects such as looseness and shrinkage holes.

[0048] Next, the center of the tube sheet forging needs to be ultrasonically inspected. After the inspection, if the tube sheet forging is qualified, there is no need to reforge the tube sheet forging; if the tube sheet forging is unqualified, it is necessary to reforge the tube sheet forging, and the reforging process is specifically introduced in Example 2.

[0049] Embodiment 2:

[0050] After the ultrasonic test of Example 1, the tube sheet forging with defects in the center will be detected. The tube sheet forging reforging process provided in Example 2 can improve the defects in the center of the tube sheet forging.

[0051] A tube sheet forging reforging process comprises the following steps:

[0052] (1) Heating the tube sheet forging: In order to facilitate the forging of tube sheet forgings with defects in the center, it is necessary to use a heating device to heat the tube sheet forging. The plasticity of the heated tube sheet forging is improved, making it easier to forge the tube sheet forging.

[0053] Specifically, a gas heating furnace may be used to heat the tube sheet forging.

[0054] Specifically, the heating temperature is 1220-1280°C. In this heating temperature range, it is more conducive to improving the activity of atoms, which is more conducive to welding defects in the subsequent forging deformation step. If the heating temperature is lower than this range, the activity of atoms will decrease, which will be unfavorable for welding defects. If the heating temperature is higher than this range, the tube sheet forging will be overheated or overburned, which will significantly reduce the plasticity and impact toughness of the tube sheet forging, thereby hindering the smooth welding of defects and reducing the forging effect.

[0055] Specifically, the heating and holding time is ≥ A×D, where A=1h / 100mm, that is, at a temperature within 1220-1280°C, the holding time for each 100mm thick tube sheet forging is 1h; D is the thickness of the tube sheet forging, in mm.

[0056] (2) Forging deformation: In order to make the internal structure of the heated tube sheet forging more compact and to heal defects such as porosity and shrinkage, forging equipment is required to forge the heated tube sheet forging.

[0057] Before forging the tube sheet forging to deform the tube sheet forging, it is necessary to cover the surface of the tube sheet forging with a thermal insulation layer. When forging the tube sheet forging to deform the tube sheet forging, the surface of the tube sheet forging covered with the thermal insulation layer can be subjected to forging by the forging equipment. The provision of the thermal insulation layer can reduce and slow down the heat dissipation of the tube sheet forging that has just been heated in step (1), thereby allowing the atoms inside the tube sheet forging to maintain a high activity for a long time, and then helping to weld the internal defects of the tube sheet forging during the forging process. Under the same forging conditions, the better the thermal insulation effect of the tube sheet forging, the better the effect of welding the internal defects of the tube sheet forging.

[0058] In addition, when forging the tube sheet forging to deform the tube sheet forging, it is necessary to maintain the pressure for a period of time each time forging, so that the internal defects of the tube sheet forging have sufficient time to be welded. Under the same forging conditions, the longer the pressure holding time, the better the welding effect of the internal defects of the tube sheet forging.

[0059] Furthermore, when forging the tube sheet forging to deform the tube sheet forging, it is necessary to make the height deformation of the tube sheet forging large enough each time so that the internal defects of the tube sheet forging can be fully welded. Under the same forging conditions, the greater the height deformation, the better the welding effect of the internal defects of the tube sheet forging.

[0060] Therefore, under the combined effect of setting up a thermal insulation layer, having a sufficient pressure holding time, and having a sufficient amount of height deformation, the internal defects of the tube sheet forging can be fully welded, and the internal defects of the tube sheet forging can be healed and improved.

[0061] Preferably, the insulation layer can be made of rock wool, foam glass board, phenolic board, foam glass board, etc. In this embodiment, rock wool is preferably used because rock wool has good insulation effect, high cost performance, and is easy to purchase.

[0062] Preferably, the holding time is ≥10 min. If the holding time is less than 10 min, the internal defects of the tube sheet forging cannot be completely welded, thereby reducing the welding effect, which will be unfavorable for reducing scrap.

[0063] Preferably, the height deformation of the tube sheet forging is ≥10%. If the height deformation is less than 10%, the internal defects of the tube sheet forging cannot be completely welded, which will reduce the welding effect and will be unfavorable to reduce scrapping.

[0064] The forging equipment includes an upper anvil for forging a tube sheet forging and a workbench for supporting the tube sheet forging. The surface of the upper anvil and the surface of the workbench are both flat, and the upper anvil covers the area with defects inside the tube sheet forging.

[0065] The reason why the surfaces of the upper anvil and the workbench are flat is that it can better compact the defects in the center of the forged tube sheet forgings and make the surface of the forgings smoother, so as to reduce the processing intensity of rough machining and fine machining of the tube sheet forgings.

[0066] The reason why the upper anvil covers the defective area inside the tube sheet forging is that if the defect range of the tube sheet forging cannot be covered, the position of the tube sheet forging needs to be adjusted many times, which makes the forging operation cumbersome and reduces work efficiency. In addition, the more cumbersome the operation is, the more the temperature of the tube sheet forging is lost, the lower the welding effect will be, which will reduce the effect of the modified forging.

[0067] Specifically, the forging equipment can be a hydraulic press, which includes an upper anvil and a lower anvil, wherein the upper anvil of the hydraulic press is used for forging the tube sheet forgings, and the lower anvil of the hydraulic press is used for supporting the working table of the tube sheet forgings.

[0068] Specifically, the surfaces of the upper anvil and the lower anvil of the hydraulic press need to be flat, and the flatness of the plane is ≤1mm.

[0069] Specifically, the upper anvil of the hydraulic press needs to cover the range of defects inside the tube sheet forging. More specifically, in order for the upper anvil to cover the defective parts as much as possible, the ratio of the diameter size of the upper anvil to the diameter size of the defective range is ≥1.1.

[0070] (3) Heating and diffusion: After the tube sheet forging is deformed by forging in step (2), it is necessary to immediately send the tube sheet forging into a heating device for heating. Heating can further diffuse the atoms near the welding position, thereby making the welding firm, improving the strength and quality of the welding, and thus improving the effect of improving defects.

[0071] Preferably, the heating temperature is 1220-1280°C. In this heating temperature range, it is more conducive to improving the activity of atoms, thereby improving the welding effect. When the heating temperature is lower than this range, the activity of atoms decreases, and the ability to improve the welding effect is limited. If the heating temperature is too high, the tube sheet forging will be overheated or overburned, which will significantly reduce the plasticity and impact toughness of the tube sheet forging, thereby hindering the smooth welding of defects and reducing the forging effect.

[0072] Preferably, the heating and heat preservation time is ≥ 8h. If the heat preservation time is less than 8h, the defects may not be completely welded, resulting in a small amount of excessive defects in the center.

[0073] Specifically, the heating equipment may also be a gas heating furnace.

[0074] After the heating and diffusion is completed, the tube sheet forging is taken out of the heating equipment and cooled.

[0075] Preferably, air cooling is used as the cooling method because of its fast cooling speed and high efficiency.

[0076] In addition, during air cooling, the temperature of the tube sheet forging surface needs to be 300-500℃. If it is lower than this temperature range, the temperature of the tube sheet forging will be too low, and white spot defects will appear inside the tube sheet forging due to the precipitation of hydrogen atoms. After air cooling to 300-500℃ on the surface, post-forging heat treatment is required.

[0077] (4) Post-forging heat treatment: The tube sheet forgings after heating and diffusion are subjected to normalizing and tempering heat treatments in sequence. Normalizing and tempering have no effect on the looseness and keyhole defects in the center of the tube sheet forgings. Their purpose is to refine the grains and prepare for ultrasonic testing.

[0078] After the reforging process of the above steps (1) to (4), a reforged tube sheet forging can be obtained.

[0079] In order to determine whether the defects in the central part of the tube sheet forging after reforging have been improved, it is necessary to perform ultrasonic testing on the tube sheet forging after reforging.

[0080] The following is a comparison table of ultrasonic testing before and after forging:

[0081] Among them, for the tube sheet forging after reforging, the defect wave reflected on the fluorescent screen during ultrasonic flaw detection is gentle, which can indicate that there are no defects in the tube sheet forging after reforging.

[0082]

[0083] Therefore, the tube sheet forging reforging process provided by the present invention can reforge tube sheet forgings with macro defects such as looseness and shrinkage holes in the central part, so that the macro defects such as looseness and shrinkage holes can be welded through high temperature and high pressure deformation to improve defects and reduce scrapping, thereby reducing costs and saving resources.

[0084] Embodiment 3:

[0085] After ultrasonic testing, a batch of tube sheet forgings made of SA508-3 material forged by our company (i.e. the applicant) were found to have continuous and dense defects in the area of ​​about Φ600mm in the center of some tube sheet forgings, exceeding the standard requirements of ASMEⅧDiv.2, resulting in the scrapping of the tube sheet forgings.

[0086] The outer diameter of this batch of tube sheet forgings is 3300mm, the height is 260mm, and the blanking weight is 18.5 tons. In order to reduce scrap losses, the reforging process in Example 2 is used for reforging, and the specific steps are as follows:

[0087] (1) Heating the tube sheet forgings: Use a gas heating furnace to heat the scrapped tube sheet forgings at a heating temperature of 1250° C. and a holding time of 4 h (A=1 h / 100 mm, D=260 mm, A×D=2.6 h, a value greater than or equal to 2.6 h is taken, and 4 h is taken in this embodiment).

[0088] (2) Forging deformation: When forging tube sheet forgings using a hydraulic press, the surface flatness of the upper and lower anvils of the hydraulic press is ≤1mm. The upper anvil with a forging surface diameter of 1.5m is used (or, when the forging surface of the upper anvil is square or rectangular, the upper anvil with a width of 1.5m is used), which is sufficient to cover the defect range of about Φ600mm in the center of the forging (the ratio of 1.5m to 600mm is 2.5, and 2.5 is greater than 1.1).

[0089] Before forging the tube sheet forging, the surface of the tube sheet forging is covered with rock wool. When forging the tube sheet forging, it is necessary to maintain the pressure for 15 minutes each time, and the height of the tube sheet forging needs to be upset from 260mm to 220mm, and the height deformation is about 15%.

[0090] (3) Heating and diffusion: After the tube sheet forging is deformed by forging in step (2), it is necessary to immediately send the tube sheet forging into a gas heating furnace for heating. The heating temperature is 1250°C and the temperature is kept at 1250°C for 10 hours. After the heating is completed, the tube sheet forging is taken out of the gas heating furnace and air-cooled until the surface of the tube sheet forging is about 300°C.

[0091] (4) Post-forging heat treatment: The tube sheet forgings after heating and diffusion are subjected to normalizing and tempering heat treatments in sequence. The normalizing temperature is 920°C and the holding time is 12 hours. The tempering temperature is 660°C and the holding time is 20 hours.

[0092] After the reforging process of the above steps (1) to (4), a reforged tube sheet forging can be obtained.

[0093] In order to determine whether the defects in the center of the tube sheet forging after reforging have been improved, it is necessary to conduct ultrasonic testing on the tube sheet forging after reforging. The results of ultrasonic testing show that there is no defect wave display in the center of the tube sheet forging, indicating that the defects in the center of the tube sheet forging have been completely healed.

[0094] The feasibility of the tube sheet forging reforging process provided by the present invention can be verified through the actual test of this embodiment 3. The tube sheet forging reforging process provided by the present invention can reforge the tube sheet forging with macro defects such as looseness and shrinkage holes in the center, so that the macro defects such as looseness and shrinkage holes are formed and welded, thereby improving the defects and reducing scrapping, thus solving the problem of high scrapping rate of tube sheet forgings.

[0095] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A tube sheet forging reforging process, characterized in that: The following steps are involved: (1) Use a heating device to heat the tube sheet forging with internal defects, the temperature of the heated tube sheet forging is 1220-1280°C; the holding time of the heated tube sheet forging is ≥A×D; where A=1h / 100mm; D is the thickness of the tube sheet forging, in mm; (2) Cover the surface of the heated tube sheet forging with an insulation layer, and forge the tube sheet forging using a forging machine. Each time the forging machine forges the tube sheet forging, the height deformation of the tube sheet forging needs to be greater than or equal to 10%, and the holding time needs to be greater than or equal to 10 minutes, so that the internal defects of the tube sheet forging can be welded; The forging equipment includes an upper anvil for forging a tube sheet forging and a workbench for supporting the tube sheet forging, the upper anvil covers the defective area inside the tube sheet forging, and the surface of the upper anvil and the surface of the workbench are both flat; (3) using a heating device to heat the tube sheet forging after forging, the temperature of the tube sheet forging after heating is 1220-1280°C, and the heating and holding time of the tube sheet forging is greater than or equal to 8 hours, so that the atoms at the welding position inside the tube sheet forging diffuse, and cooling is performed after the heating is completed; (4) The cooled tube sheet forging is subjected to post-forging heat treatment.

2. A tube sheet forging reforging process as claimed in claim 1, characterized in that: In step (2), the thermal insulation layer is made of rock wool.

3. A tube sheet forging reforging process as claimed in claim 1, characterized in that: In the step (3), air cooling is used for cooling after heating until the surface temperature of the tube sheet forging is 300-500°C.

4. A tube sheet forging reforging process as claimed in claim 1, characterized in that: In the step (4), the post-forging heat treatment includes normalizing treatment and tempering treatment in sequence.

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